Quick fix

app/datatables/stock_by_pointsale_datatable.rb

@@ -43,7 +43,7 @@ class StockByPointsaleDatatable
           available.stock_max.round,
           available.stock.round
         ]
-        arr += get_price_sale(available.product) unless @current_user.usertype == "S"
+        arr << get_price_sale(available.product) unless @current_user.usertype == "S"
         arr.compact
       end
     end